The Benefits of Fasted Cardio – Does it Work to Train on an Empty Stomach?

No matter what gym or fitness center you go to, one theory you are bound to hear about is fasted cardio. Fasted cardio involves performing a cardiovascular exercise – usually high-intensity exercise — on an empty stomach, typically first thing in the morning. The theory of fasted cardio, according to the people that practice it regularly, is that you will burn fat faster.

This belief originates with a study in the British Journal of Nutrition not too long ago that suggested you burn 20% more fat when you fast and do cardiovascular exercise in the morning. It almost sounds like common sense, doesn’t it? After all, by the time you wake up in the morning, you’ve probably had nothing to eat for at least 10 hours, and probably closer to 12. Since it’s out of fuel, your body has to get it somewhere.

That’s what fat is: Stored energy. When you’re out of fuel, the body starts looking for stored fuel in the form of fat. So you might thing that performing intense cardiovascular exercise on an empty stomach would be the go-to way to burn a lot of fat and lose weight.

Though the results sound good, let’s dive into this and think about what that really means.

Should You Exercise On an Empty Stomach?

There are a number of reasons why you need to think long and hard about doing fasted cardio. The short answer here is maybe, and we will look at why we say that instead of giving you a firm yes or no. If you plan to do your cardio routine in a fasted state, we recommend doing so using High-Intensity Interval Training (otherwise known as HIIT). People have reported almost double the fat loss doing HIIT versus other types of cardio and frankly, we recommend doing HIIT instead of most “slow and steady” routines.

You can even use simple routines like these in a pinch if you can’t get to the gym to train with actual weights.

So just how does fasted cardio work? While you’re sleeping your body converts fat and amino acids into glucose, which it uses as fuel. The thought is that training right away when you wake up immediately puts your body at a caloric deficit, forcing it to reach for the fat stores before it reaches for any recently ingested nutrients from food you’ve eaten for breakfast. While this theory hits the mark for many people, you can potentially actually be burning muscle when you’re doing high-intensity workouts while fasting if you aren’t careful about getting the right nutrients through your day.

If you are trying to increase muscle mass, you should not do extensive HIIT or intense cardio in a fasted state. Most of the time, we recommend only doing three sessions of cardio per week for no more than 20 minutes when you are trying to gain muscle mass instead of burn fat.

Light cardio is fine to get your heart moving, but the goal of gaining muscle requires a calorie surplus while losing fat requires a caloric deficit. If your goal is to gain muscle, make sure you limit your cardio to nothing more than a warm-up.

If your primary goal is to lose fat, fasted cardio can work. Not every person will get the same results when testing the exact same exercise methods, but are many men and women on the health forums that will swear buy it. There’s also plenty that say that it’s just not for them because they feel the lack of energy without taking in at least some type of food before exercising.

Some of the Pros of Fasted Cardio:

While there are are plenty of suggested scientific pros to doing your cardio in a fasted state, we are going to cover some of the primary reasons that most people actually say that they see as a benefit from fasted cardio.

Training on an Empty Stomach gives people a little freedom with your first meal as long as it fits your macronutrients for the day.

People that are already somewhat lean tend to report that they lose fat faster by incorporating HIIT and fasted cardio.

People that support fasted cardio say they see a more visual fat loss in a quicker time period.

Some of the Cons of Fasted Cardio:

Some people report feeling weak due to having a lower blood sugar level.

Training in a fasted state is difficult for beginners. It’s a tactic that may be better reserved for people that have been exercising in a consistent routine for at least 90 days.

Some individuals report “falling off the wagon” after their session and binge eating because they felt they gave themselves a little bit more of a “cheat.”

Our Final Thoughts:

Fasted Cardio can work, but like any fitness routine, it depends on your fitness level, exercise regimen and overall diet to really see it make a difference. If you are just incorporating an exercise routine into your daily lifestyle, focus on the basics like finding full body compound exercises and a training routine that you enjoy, finding the foods that will make you stick to your plan and finding people that will support and encourage you hitting your goals.

If you are a fitness vet, test it out and see how you feel. Many people report great results and it just might be the method that helps you hit your fat loss goals.